The present invention relates to a mobile type non-contact power feeding device, and more particularly to a non-contact power feeding device adapted to feed power, with no contact, to a moving secondary side, that is, a power receiving side or a pickup side from a stationary primary side, that is, a power feeding side or a track side.
A non-contact power feeding device adapted to feed power to, for example, a battery of an electric vehicle without any mechanical contact such as a cable has been developed based on the demand and this device is in practical use.
In this non-contact power feeding device, power is fed through an air gap in a closely corresponding manner to a power receiving coil of a power receiving side mounted on a movable body such as an electric vehicle from a stationary power transmission coil of a power feeding side based on a mutual induction effect of electromagnetic induction.
A stopped type power feeding method is a representative example for feeding power by the non-contact power feeding device, but a convenient mobile type power feeding method which is not required to purposely stop for power feeding has also been developed and this method is in practical use.
Referring to the stopped type power feeding method, the movable body is required to stop in the case of power feeding and the power receiving coil is positioned to stop on or over the power transmission coil to feed power. On the contrary, in the mobile type power feeding method, the movable body is not required to stop in the case of power feeding and power feeding is effected while the power receiving coil is moving near the power transmission coil.
The technology disclosed in the following Japanese Unexamined Patent Publication No. H06-506099 (Japanese translation of PCT international application) is a representative example of a mobile type non-contact power feeding device.
However, this non-contact power feeding device is suitable for an automated guided vehicle which is used in a factory and the like, but there is a disadvantage that it is not suitable for use in an electric vehicle which is running on a road. In other words, the power receiving coil of the power receiving side is required to move through an extremely-close small air gap relative to the stationary power transmission coil of the power feeding side.
In order to overcome such a disadvantage of the non-contact power feeding device as disclosed in Japanese Unexamined Patent Publication No. H06-506099 (Japanese translation of PCT international application), the technologies disclosed in the following Japanese Unexamined Patent Publication No. 2002-508916 (Japanese translation of PCT international application) and Japanese Unexamined Patent Publication No. 2009-501510 (Japanese translation of PCT international application) have been developed.
The technologies disclosed in Japanese Unexamined Patent Publication No. 2002-508916 (Japanese translation of PCT international application) and Japanese Unexamined Patent Publication No. 2009-501510 (Japanese translation of PCT international application) are characterized in that an independent repeating circuit is provided to serve as a resonant circuit on a power feeding side and/or a power receiving side, and a repeating coil of the resonant circuit is disposed in a magnetic path of the air gap. With this arrangement, the mobile type non-contact power feeding device composed of this resonant repeating method enables power supply through a large air gap and is suitable for feeding power to, for example, an electric vehicle.
It has been pointed out that the mobile type non-contact power feeding device has the following problems.
In the non-contact power feeding device, power feeding is conducted based on a mutual induction effect of electromagnetic induction. Since a high frequency magnetic field (an alternate-current variable magnetic field) is strongly formed to radiate and diffuse high frequency electromagnetic waves at a strong intensity, there is a possibility that this has an adverse affect on the neighboring environment.
For example, in an area which is tens of meters to hundreds of meters away, it has been pointed out that there is a risk that electromagnetic pollution such as possible electromagnetic disturbance and electronic jamming are caused and a risk that dysfunction is created on human bodies.
Under these circumstances, for example, in Japan, the Radio Law sets limits on facilities where a high frequency of 10 kHz or more is used to make the intensity of electromagnetic waves radiated from these facilities less than or equal to the regulatory value.
On the contrary, in the case of the stopped type non-contact power feeding device described above, it is easy to take measures for electromagnetic shielding. In other words, since a loop of the power transmission coil of the power feeding side is small, by covering the power transmission coil with an electromagnetic-wave shielding cover in which an electrically conductive material is used, it is easy to reflect, absorb and attenuate the radiated electromagnetic waves to the regulatory value level or lower.
On the contrary, in the case of the mobile type non-contact power feeding device, it is difficult to take measures for the electromagnetic shielding.
In other words, the power transmission coil of the power feeding side, in view of the fact that the power receiving side is moving, is formed in a long and massive loop shape along the direction of movement and has a large loop area. In this manner, it is not easy to take such an electromagnetic shielding measure as to cover the power transmission coil with the electromagnetic shielding cover and as a result, it is easy for the radiated electromagnetic waves to reach a neighboring area.
Accordingly, a conventional mobile type non-contact power feeding device has been set and used in a range in which the usable frequency does not exceed the regulatory value, that is, 10 kHz.
Referring to the non-contact power feeding device, expansion of an air gap is a major theme in view of the needs such as widespread utilization of the electric vehicles.
Even in the mobile type non-contact power feeding device, the technologies disclosed in Japanese Unexamined Patent Publication No. 2002-508916 (Japanese translation of PCT international application) and Japanese Unexamined Patent Publication No. 2009-501510 (Japanese translation of PCT international application) described above have been developed in view of such needs and themes, but because of adoption of the resonant repeating method, those technologies are premised on the use of a high frequency AC of 10 kHz or more, for example, a high frequency AC of the degree of tens of kHz to 100 kHz, from the aspect of efficiency.
Accordingly, if this mobile type non-contact power feeding device is adopted, as is, to feed power to an electric vehicle which is running on an express highway or other roads, the electromagnetic waves radiated outside become stronger to have a greater risk of generating the electromagnetic pollution described above. It is therefore quite difficult to adopt the mobile type non-contact power feeding device under the existing conditions because of the problems described above.